diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index b4eea229b8e..4023362a4ec 100644
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -1020,9 +1020,14 @@ func (check *Checker) index(index ast.Expr, max int64) (typ Type, val int64) {
 		return x.typ, -1
 	}
 
-	v, valid := constant.Int64Val(constant.ToInt(x.val))
-	if !valid || max >= 0 && v >= max {
-		check.errorf(&x, _InvalidIndex, "index %s is out of bounds", &x)
+	if x.val.Kind() == constant.Unknown {
+		return
+	}
+
+	v, ok := constant.Int64Val(x.val)
+	assert(ok)
+	if max >= 0 && v >= max {
+		check.invalidArg(&x, _InvalidIndex, "index %s is out of bounds", &x)
 		return
 	}
 
diff --git a/src/go/types/testdata/expr3.src b/src/go/types/testdata/expr3.src
index c3158e6cf41..0525a5a33ae 100644
--- a/src/go/types/testdata/expr3.src
+++ b/src/go/types/testdata/expr3.src
@@ -34,6 +34,7 @@ func indexes() {
 	_ = a[9]
 	_ = a[10 /* ERROR "index .* out of bounds" */ ]
 	_ = a[1 /* ERROR "overflows" */ <<100]
+	_ = a[1<< /* ERROR "constant shift overflow" */ 1000] // no out-of-bounds follow-on error
 	_ = a[10:]
 	_ = a[:10]
 	_ = a[10:10]